We will test a model of pediatric office-based intervention to reduce the frequency of alcohol and tobacco use by young adolescents and their parents in a randomized trial of 3,300 fifth and sixth graders and their parents in ten New Hampshire pediatric practices. Children and their parents will receive the intervention and complete annual questionnaires for 36 months. The intervention will include discussions with the pediatrician about each family's alcohol and tobacco use; a course for parents; a communication game and videotapes for parents and children; regular newsletters; and other reinforcing contacts. High risk children and their parents will receive a more intensive intervention and more frequent follow-up. We will monitor school and community prevention activities in the ten catchment areas to assess confounding.